1. Field of the Invention
The present invention relates in general to a control device for controlling operation of an internal combustion engine, and more particularly to a valve timing control device which controls or varies an open/close timing of intake and/or exhaust valves of the internal combustion engine in accordance with an operation condition of the engine.
2. Description of the Related Art
In order to clarify the task of the present invention, one valve timing control device of an internal combustion engine will be briefly described, which is shown in Laid-open Japanese Patent Application (Tokkai-hei) 10-153104.
In the valve timing control device of the publication, a timing pulley driven by a crankshaft of the engine is rotatably disposed around a shaft member which is integrally connected to a camshaft. A so-called xe2x80x9crelative rotation angle control mechanismxe2x80x9d is arranged between the timing pulley and the shaft member. The relative rotation angle control mechanism comprises generally a piston member which is axially movably connected to the timing pulley while being suppressed from rotating about an axis thereof relative to the timing pulley, a first helical gear which is formed on a cylindrical inner surface of the piston member, a second helical gear which is formed on a cylindrical outer surface of the shaft member and meshed with the first helical gear and an electric actuator which moves the piston member axially. The electric actuator comprises electromagnets and a return spring. That is, by moving the piston member forward or rearward to a desired position by the electric actuator, a relative rotation angle between the timing pulley and the shaft member is controlled or varied.
However, in the above-mentioned valve timing control device of the publication, due to the arrangement wherein the piston member is moved forward or rearward along the axis of the camshaft, the parts arranged at the front end of the camshaft need an axially enlarged mounting space thereof, which brings about an increase in length of the engine. In fact, the electromagnets of the electric actuator arranged at an axially outside area of the piston member induce a major cause of the increase of the axially enlarged mounting space of the valve timing control device.
For solving such shortcoming of the 10-153104 publication, various measures have been proposed and put into practical use. Some of them are of a type employing an electromagnetic brake which, when energized, produces a braking force for braking a movable part of the valve timing control device to provide the camshaft with an adjusted (viz., advanced/retarded) rotation angle relative to the crankshaft. However, in some of them, usage of such electromagnetic brake has induced a wasteful electric power consumption of the vehicle.
It is therefore an object of the present invention to provide a valve timing control device of an internal combustion engine, which is free of the above-mentioned drawbacks.
That is, according to the present invention, there is provided a valve timing control device of an internal combustion engine, which can reduce or save an electric power consumed by an electromagnetic brake employed for applying an operation force to a movable control member of the valve timing control device.
According to a first aspect of the present invention, there is provided a valve timing control device of an internal combustion engine, which comprises a drive rotation member rotated about a given axis by a crankshaft of the engine; a driven rotation member rotated about a given axis together with a camshaft of the engine; a relative rotation angle control mechanism through which the drive and driven rotation members are coaxially connected, the relative rotation angle control mechanism having a movable control member which, when applied with an operation force from an actuation device, varies a relative rotation angle between the drive and driven rotation members, the actuation device comprising a first electromagnetic brake which applies an operation force to the movable control member to cause a rotation of the driven rotation member to be shifted in one of advancing and retarding directions with respect to a rotation of the drive rotation member; and a second electromagnetic brake which applies a operation force to the movable control member to cause the rotation of the driven rotation member to be shifted in the other of the advancing and retarding directions with respect to the rotation of the drive rotation member.
According to a second aspect of the present invention, there is provided a valve timing control device of an internal combustion engine, which comprises a drive rotation member rotated about a given axis by a crankshaft of the engine; a driven rotation member rotated about the given axis together with a camshaft of the engine; a relative rotation angle control mechanism through which the drive and driven rotation members are coaxially connected, the relative rotation angle control mechanism having a movable control member which, when radially moved by receiving an operation force, varies a relative rotation angle between the drive and driven rotation members; and an actuation device which applies an operation force to the movable control member, the actuation device comprising a first electromagnetic brake which applies an operation force to the movable control member to cause a rotation of the driven rotation member to be shifted in one of advancing and retarding directions with respect to a rotation of the drive rotation member; and a second electromagnetic brake which applies a operation force to the movable control member to cause the rotation of the driven rotation member to be shifted in the other of the advancing and retarding directions with respect to the rotation of the drive rotation member, the relative rotation angle control mechanism comprising an intermediate rotation member rotatable about the given axis relative to both the drive and driven rotation members, the intermediate rotation member being formed with a spiral guide with which the movable control member is slidably engaged, so that rotation of the intermediate rotation member induces the radial movement of the movable control member.
According to a third aspect of the present invention, there is provided a valve timing control device of an internal combustion engine, which comprises a drive rotation member rotated about a given axis by a crankshaft of the engine; a driven rotation member rotated about the given axis together with a camshaft of the engine; a relative rotation angle control mechanism through which the drive and driven rotation members are coaxially connected, the relative rotation angle control mechanism having a movable control member which, when radially moved by receiving an operation force, varies a relative rotation angle between the drive and driven rotation members; and an actuation device which applies an operation force to the movable control member, the actuation device comprising a first electromagnetic brake which applies an operation force to the movable control member to cause a rotation of the driven rotation member to be shifted in one of advancing and retarding directions with respect to a rotation of the drive rotation member; and a second electromagnetic brake which applies a operation force to the movable control member to cause the rotation of the driven rotation member to be shifted in the other of the advancing and retarding directions with respect to the rotation of the drive rotation member, the relative rotation angle control mechanism comprising an intermediate rotation member rotatable about the given axis relative to both the drive and driven rotation members, the intermediate rotation member being formed with a spiral guide with which the movable control member is slidably engaged, so that rotation of the intermediate rotation member induces the radial movement of the movable control member; and a link through which the movable control member is linked to a given portion of the driven rotation member, the given portion being positioned away from the given axis in a radial direction.
According to a fourth aspect of the present invention, there is provided a valve timing control device of an internal combustion engine, which comprises a drive rotation member rotated about a given axis by a crankshaft of the engine; a driven rotation member rotated about the given axis together with a camshaft of the engine; a relative rotation angle control mechanism through which the drive and driven rotation members are coaxially connected, the relative rotation angle control mechanism having a movable control member which, when radially moved by receiving an operation force, varies a relative rotation angle between the drive and driven rotation members; and an actuation device which applies an operation force to the movable control member, the actuation device comprising a first electromagnetic brake which applies an operation force to the movable control member to cause a rotation of the driven rotation member to be shifted in one of advancing and retarding directions with respect to a rotation of the drive rotation member; and a second electromagnetic brake which applies a operation force to the movable control member to cause the rotation of the driven rotation member to be shifted in the other of the advancing and retarding directions with respect to the rotation of the drive rotation member, the relative rotation angle control mechanism being so arranged that when both the first and second electromagnetic brakes of the actuation device become deenergized, a certain relative rotation angle is provided between the drive and driven rotation members, which is suitable for starting of the engine.
Other objects and features of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings.